Drug reference

Foscarnet

Antiviral

Also known as Foscarnet sodium

AntiviralATC J05AD01

CDSCO approvedSchedule HATC J05AD01

EXCRETION

—

not curated

INTERACTIONS

12 major

SEVERE in our sources

PREGNANCY

Manufacturer advises avoid.

FDA category + note

Top interactionssee all 12 →

AmikacinSevereDatabaseDDInter
AmiodaroneSevereDatabaseDDInter
AmisulprideSevereDatabaseDDInter
Amphotericin BSevereDatabaseDDInter

Mechanism

Foscarnet (phosphonoformic acid) is an inorganic pyrophosphate analogue that directly inhibits viral DNA polymerase and HIV reverse transcriptase by binding to the pyrophosphate-binding site, blocking cleavage of pyrophosphate from deoxynucleoside triphosphates. Critically, it does not require intracellular phosphorylation by viral thymidine kinase, making it effective against acyclovir-resistant HSV and ganciclovir-resistant CMV strains that carry thymidine kinase or UL97 kinase mutations.

Indications

Mucocutaneous herpes simplex virus infection unresponsive to aciclovir in immunocompromised patientsCytomegalovirus infectionall herpesvirusesHIVCMV retinitis (including ganciclovir-resistant infections)other types of CMV infectionacyclovir-resistant HSV and VZV infectionspreemptive therapy of CMV viremia in bone marrow transplant recipientsacyclovir-resistant mucocutaneous HSV infectionscytomegalovirus retinitisCMV retinitis and other CMV infections in AIDS patients (including ganciclovir-resistant)acyclovir-resistant mucocutaneous H. simplex type 2 and varicella-zoster infections in AIDS patientsTreatment of CMV-related CNS infections

Dosing

Adult: Inosine pranobex p. 670 has been used by mouth for herpes simplex infections; its effectiveness remains unproven. Cytomegalovirus infection Ganciclovir p. 674 is related to aciclovir but it is more active against cytomegalovirus (CMV); it is also much more toxic than aciclovir and should therefore be prescribed only when the potential beneﬁt outweighs the risks.…

Pharmacokinetics

Half-life

4 to 8 h (initial bimodal half-lives); 3 to 4 days (prolonged terminal elimination t1/2 due to sequestration in bone)

Bioavailability

Low (oral)

Protein binding

14–17%

Metabolism

Not metabolised

Excretion

Over 80% excreted unchanged in the urine; cleared efficiently by hemodialysis (~50%)

Side effects

Common

nephrotoxicity (up to one-half of patients)increases or decreases in Ca2+ and phosphatehypomagnesemiahypokalemiaheadache (25%)tremorirritabilitygeneralized rashfevernauseaemesisanemialeukopeniaabnormal liver function testselectrocardiographic changesinfusion-related thrombophlebitispainful genital ulcerationslocal irritation (topical)ulceration (topical)gastrointestinal disturbance (oral)visual disturbanceconjunctivitishypersensitivityFatiguetoxicity

Serious

Renal impairment
symptomatic hypocalcemia
seizures
hallucinosis
kidney damage (renal diabetes like condition, acute renal failure)
anaemia
phlebitis
tremor
convulsions
neurological symptoms due to hypocalcaemia
constitutional symptoms due to hypocalcaemia
Renal impairment (~one-third of patients), often associated with elevations in serum creatinine and proteinuria (reversible in most cases)
Reductions in serum calcium, magnesium, and potassium (~15%), potentially associated with tetany, cardiac rhythm disturbances, or seizures
renal dysfunction
hypomagnesemia
hypokalemia
hypocalcemia
genital ulcers
dysuria
nausea
paresthesia